Pilot burner and thermocouple therefor



S, 1958 A w. F. .JACKSON Erm. 2,333v343 PILOT BURNER ymm 'mERMocouPLETHEREFOR Filed oct. 15, 1954 v 2 sheets-sheet 1 12 14H1: l@ j j I"\ l 22S E l i l S f z l t r l i s j* @5mm mmomw ay 9 i958 w. F. JACKSON Erm.839%3 PILOT BURNER AND THERMOCOUPLE THEREFOR Filed ooi. 15. 1954 2Sheets-Sheet 2 INVTORSv Patented May 6, 1958 PILOT BURNER ANDTHERMOCUUPLE THEREFOR Application October 15, 1954, Serial No. 462,502

4 Claims. (Cl. 13G-4) This invention relates to a combination pilotburner and thermocouple generator unit and more particularly to such aunit employing a pilot burner of the non-primary aerated type.

In the past, thermostatic safety control devices depended entirely upona pilot burner which was separated from its correlated thermocouple andjoined therewith by a comon mounting means. In these combinations, thepilot burner consumed a relatively large amount of fuel in the two-foldfunction of igniting the main burner and playing upon, at most, a smallportion of the thermocouple in order to maintain energization of anelectromagnet for maintaining a fuel supply valve member in openposition. These devices were handicapped in that a relatively largepilot burner was needed in order to produce a ame adequate for heatingthe thermocouple which was located in the path of only a small portionof the flame.

Besides being bulky, expensive, overly gas consuming, and requiring manyinstalling manipulations to effect replacement, these combinationsproduced what is referred to as hot range and hot kitchen conditions.The ame emanating from the pilot burner, when the main burners of therange were not in use, was so great that a marked rise in temperaturecould be observed in the range structure and in the immediate vicinity.

In very recent years, the advent of pilot burner-thermocouple unitssolved many of the former problems, but reduced the disadvantages onlyto a slightly less degree. Such units included a small thermocouplehoused within the pilot burner casing and required a small ame which wassucient for heating a thermocouple hot junction. These units although astep toward ultimate perfection in the use of pilot burners andthermostatic safety devices are still deficient in eliminating the maindisadvantages presently found in the conventional separated pilotburner-thermocouple systems.

The pilot burner-themocouple unit, of late, utilizes a gas and airmixture or primary aerated mixture in much the same manner as formerlyand therefore is subject to all the disadvantages encountered with suchmixture. In preparing a gas-air mixture, use is made of an orifice ofextremely close tolerances to permit the passage of the proper amount ofgas into a mixing chamber. Since the flow of gas through the orifice isvery sensitive to the area of the opening, a slight amount of cloggingthereat would immediately aifect the amount of gas entering the mixingchamber resulting in a serious contraction of the burner llame which maynot be capable thereafter of igniting the main burner.

In much the same manner, the primary air iiowing in the passageway tothe mixing chamber must be properly protected against linting and anysuch clogging of the passageway would immediately manifest itself at theflame tip of the pilot burner. Manufacture and installation of an oriceof exact tolerances as well as the fabrication of a lint filter hasgreatly increased the cost of the present day unit. Further, since theoritices in l?v these units are sensitive to varying conditions, theorifices may have to be replaced in orderr to accommodate dif-` ferenttypes of domestic gases with differing pressures and densities, therebyincreasing the cost of the unit and the linstallation thereof.

Another disadvantage of the present day pilot burnerthermocouple unit isthe relative high gas consumption rate and the tendency of the unit toproduce hot range or hot kitchen conditions. Although, these unitsutilize a smaller tiame than in previous embodiments of the pilotburner-thermocouple combination, there is, nevertheless, a tendency onthe part of the pilot burner to cause a hot range only to a lowerdegree.

Many unsuccessful attempts have been made toward accomplishing an idealcold range pilot burner of the type utilized for controlling athermomagnetic gas supply valve. Most notable of the solutions to theproblems involved were directed to reducing the size of the pilot burnerto insure a small flame and increase the voltage output of thethermocouple. However, the present day pilot burners, especially of thetype housing a thermocouple, are of the aerated type and these havedefinite limitations for pilot burner size in order to obtain successfuloperation. It is generally known in the art that the primary aeratedtype pilot burner has a narrow B. t. u. output range and in order tomaintain a useful flame at the burner tip,I the minimum of that rangemust be kept at a relatively high value because a certain amount of gasmust flow into the mixture chamber from the orice with suiiicientvelocity to draw air from the atmosphere for proper mixture thereof.

On tie other hand, the non-primary type pilot burner has a relativelyWide B. t. u. output range and the raw gas tiowing to the burner may beturned down to an extremely small output value to maintain a usefulflame at ythe burner tip. In operation, the raw gas literally driftsupward through the interior of the burner body and out into theatmosphere by way of suitable flame ports where the gas aerates andburns at approximately the same time. In this type of burner an outputof an extremely low number of B. t. u.s per hour can be easily achievedand still produce suicient heat to maintain a thermomagnetic valve inopen position and to ignite a main burner.

The present invention is directed to a pilot burnerthermocouple unitwhich avoids the disadvantages found in similar present day units. Tothis end, a pilot burner of the non-primary aerated type is provided andtakes the form of a tubular member surrounding an elongated thermocoupleand including a plurality of annular flame ports at one end adjacent thehot thermojunction of the thermocouple. a flow limiter is provided inthe raw gas inlet portion of the burner tubular member. Since primaryair is not required to be premixed with the gas, it is sufficient thatthe orifice be adapted to restrict somewhat the amount of gas enteringthe burner rather than allowing the gas to flow within precise limits.The burner is adapted to maintain energization of a thermomagnetic valvewhile in the open position and to ignite a main burner with an output ofrelatively low consumption. Accordingly it is an object of the presentinvention to accomplish a proper igntion of the main burner and heatingof a thermostatic safety control device employing a pilot burner whichconsumes an extremely small amount of gas at all times.

ln addition, a novel rwelding process is employed to form and insuremaximum heating of the hot thermojunction and at the same time toprevent the formation of carbon at this point. To this goal, a piece ofwire of the same material as that of one of the thermocouple elements isbutt Welded to the extreme tip of the other therrnocouple element sothat a small piece of the wire An orifice functioning in the nature ofday pilot burner-thermocouple units.

Another object of the invention is to increase the turn downcharacteristics of a pilot burner-thermocouple unit, insuring quietoperation thereof and reducing the usual inherent flash back tendenciesof the present day pilot burners.

Other objects and advantages will become apparent from the followingdescription taken in conjunction with the accompanying drawing wherein;

Fig. l is a fragmentary sectional view of the present invention in onestage of assembly; v

Fig. 2 is an enlarged fragmentary sectional viewof a detail;

Fig. 3 is a sectional view of a combination generatorpilot burnerembodying this invention; and

Fig. 4 is a sectional view taken on the lines IV-IV of Fig. 2.

Referring to Figs. 1V and 3, there is shown a thermocouple-pilot burnercombination comprising a pilot burner tubular body 1i) having aninturned end provided with a plurality of equally spaced slots 12forming flame ports. In this instance, four such ports are provided. Athermocouple, generally indicated by the reference numeral 14, isaccommodated and supported within the body 1t). d

The thermocouple 14 includes an outer thermocouple element 16 of tubularform having a reduced annular neck portion 18 projecting exteriorly ofthe burner 10 and providing an inner annular wall for the flame ports12. A rod-like inner thermocouple element 22 is positioned interiorly ofthe element 16 and has its uppermost end projecting partly into the neckportion 18 and secured in a manner to be described hereinafter. It is tobe noted that the burner body 10 and the elements 16 and 22 arepreferably arranged about a common axis with the outer element 16 beingconcentric with the burner body 10. Since the outer thermocouple element16 is of smaller diameter than the body an annular passageway 24 .isprovided therebetween and serves to transmit the tlow of raw fuel from afuel supply source (not shown) to the burner ame ports 12.

As shown in Figs. l and 2 the upper end of the inner element 22 issomewhat shorter than the neck portion 18 of the outer element 16,leaving a recess 26 at the terminal end of the neck portion 18 toaccommodate a lling material to `be described hereinafter. An annularretaining disc 28 is secured to the terminal end of the neck portion 18spaced from but overlying the burner ame ports 12 and serves to spreadthe flow of raw gas emitted by the llame ports 12. To complete thethermocouple structure, an linsulation sleeve 30 of suitable material,such as Fiberglas, is provided between the outer element 16 and theinner element 22 and terminating short of the neck portion 18.

The tubular body 10, the outer element 16 and the retaining disc 28 areall preferably made from 27% chrominum steel, the inner conductorelement 22 being made from the well known alloy constantan whichconsists of approximately 45% nickel and 55% copper. well known in theart that nickel, inthe presence of sulphur-carrying fuel gas, deposits aquantity of undesirable carbon formation on the metal due to cracking ofthe uel gas. Previous methods of welding inner and outer thermocoupleelements consisted simply of fusing the ends of the elements, such as bythe well-known Heliarc It isy viously described recess 26 as shown inFig. 2.

4 welding process until a solid junction was formed at the ends.However, since the inner thermocouple element formed part of theresulting welded junction, nickel was included therein. Consequently,fuel gas which was permitted Ato ow around the welded junction caused anappreciable formation of carbon at this point.

To eliminate such contact of gas with the nickel present in the innerelement 22, a piece of chromium steel wire 32, which is devoid ofnickel, is butt-welded at 33 to the upper extremity of the inner element22 within the pre- In that figure, a quantity of unmelted nickel-freemetal 35 from the chrominum steel wire 32 remains in the recess 26 andthe retaining disc 28, the narrow neck portion 18 and the adjacent upperportion of the wire 32 are then fused together.

The finished weld` alloy designated by theV reference numeral 34lconsists of the chromium steel furnished by the element 16, the disc 28and the nickel-free chromium steel from the adjacent portion of the wire32. Thus, an insulating body in the form of the unmelted chromium steel35 remains between the nickel-bearing' inner element 22 and the weld 34.In this manner, the thermocouple 14 is formed with a hot thermojunctionwhich comprises the rigid welded connection 33 for the upper extremityof the thermocouple element 16 and the lower portion of the wire 32. v

As shown in Fig. 3, the lower end of the tubular burner body 10 isreceived in a bore 36 formed in a burner support 38 and is weldedtherein or otherwise secured to the support 38 by any suitable means. Inorder to prevent the escape of gas between the edges of the bore 36 andthe exterior wall of the member 10, a suitable sealing material 37 isprovided therebetween and may take the form of the welding material ifthe member 10 is welded to the support 38. An angular passageway 40 isformed in the support 38 and communicates with the annular passageway 24for conducting raw fuel gas thereto. Integral with the support 38 andextending therefrom substantially parallel with the body 10 is a nipple42 which has achamber V' 44 in communication with the passageway 40., Agas sup- The lower end of the outer thermocouple element 16 is vreceived in a bore 50 formed in the lower section of the support 38 andis suitably soldered therein at 52 with silver solder. An insulated leadwire 54 is connected, axially at `56 as by silver solder, to the lowerend of the inner thermocouple element 22 to Iform the cold junction ofthe thermocouple 14. A lead tube 58 encases the insulated wire 54 and isconnected to the lower end of the element 16 by means of thegsame silversolder joint 52 used to connect `the element 16 to the support 38. Itwill be apparent that the wire 54 and the tube.58 serve as conductorsfor transmitting the electricity generated by the thermocouple 14 to anenergizing coil of ya thermomagnetic valve (not shown).

In operation, assuming that. the thermocouple-pilot burner unit, asshown in Fig. 3, is suitably connected for use in a heating appliance sothat the pilot burner body 10 is in vproper lighting relationship withthe main burner (not shown) of the appliance to which gas will besupplied under control of a thermostatic valve (not shown) so as tomaintain the appliance at a desired heating temperature, then a gas cock(not shown) is turned to the open position. This will permit the ow ofraw gas to the ame ports 12 where the gas is ignited by any conventionalmeans by way of the tube 46, the chamber 44, the passageway 40'and thepassageway 24. By reason of this invention a`relatively 'small number ofB. t. u.s per hour is consumed.

The annular ports 12 cause a circular sleeve of ame to form around theneck portion 18 of the thermocouple 14, which llame is retained andstabilized sufficiently by the retaining disc 28 to reduce thepossibility of its accidental extinguishment. The disc 28 also serves tospread the iiow of gas issuing from the ports 12 and thereby produceturbulence so that it will burn a blue flame despite the lack 0f primaryair. Further, the disc 28 offers more surface area to be heated by theflame thereby producing a better heat-conducting path to the hotthermojunction.

From the foregoing description, it will be 'apparent that by the presentinvention, a low gas consuming pilot burner has been combined with asensitive and relatively powerful thermocouple generator. Herefofore,devices of this general character have utilized a mixture of primary airand gas to serve as fuel for the pilot burner but with little success inestablishing a low gas consuming burner, because of the speed at whichthe gas must flow through an orifice in order to induce a sufficientamount of air to mix therewith. The present invention obviates thislimitation by utilizing a pilot burner of the non-aerated type which iscapable of adequately heating a built-in thermocouple even though thegas consumption is extremely low, such gas consumption being less thanthat which is possible with the aerated or Bunsen burner type.

Another feature of the present invention resides in the novel formationof the hot thermojunction wherein the nickel ingredient of the innerthermocouple element is prevented, in any way, from coming in Contactwith the surrounding atmosphere of the pilot burner unit by theprovision of an insulator in the form of an unmelted mass of chromiumstainless steel between the element and the surrounding atmosphere. Inthis way, the nickel ingredient is not liquiiied as would be the case inconventional welding processes and cannot mix with the other elements ofthe hot thermojunction so as to be exposed to the atmosphere.

While the embodiment of the invention has been shown and described withconsiderable particularity, it is to be understood that the invention isnot restricted thereto as the same is capable of receiving a variety ofmechanical expressions, as will be apparent to those skilled in the art.lt will be understood that many changes may be made in the details ofconstruction and arrangement of parts without departing from the scopeof this invention as defined in the appended claims.

We claim:

l. A method of forming the hot thermojunction for a thermocouple havingan elongated nickel-containing conductor encased in a nickel-freemetallic cylinder comprising the steps of positioning a relatively shortpiece of nickel-free metallic rod in axial alignment and in end to endabutting relationship with respect to said conductor, fusibly uniting,as by a weld, the abutting ends of said conductor and said rod,inserting said conductor and said rod into a nickel-free metalliccylinder with the united ends adjacent an open end thereof, and fusiblyuniting, as by a weld, the other end of said rod with the portion ofsaid cylinder adjacent said open end whereby said second weld iscomposed of a nickelfree alloy.

2. In a thermocouple, a first thermocouple element of nickel containingmetal, a tubular thermocouple element of nickel-free metal in radiallyspaced coaxial rel-ation to said first element and projecting beyond oneend thereof to form a recess, and an insert portion of nickel-free metalin said recess having one end Welded to said one end of said firstelement, said portion having its opposite end welded to said tubularelement leaving an unmelted section of nickel-free metal between saidfirst element and the surrounding atmosphere.

3. In a combination pilot burner and thermocouple, a first thermocoupleelement of a first metal, a tubular thermocouple element ofsubstantially nickel-free metal in radially spaced coaxial relation tosaid first element and projecting beyond one end thereof to form arecess, an insert portion of substantially nickel-free metal in saidrecess having one end welded to said one end of said first element toform a hot thermojunction, means located adjacent said thermojunctionfor directing a llame upon said projection adjacent said thermojunction,and flame retaining means of substantially nickel-free metal welded tothe opposite end of said portion and to said projection leaving anunmelted section of substantially nickel-free metal between said firstelement and the surrounding atmosphere.

4. 1n a combination pilot burner and thermocouple, a first thermocoupleelement of nickel containing metal, a tubular thermocouple element ofnickel-free metal in radially spaced coaxial relation to said firstelement and projecting beyond one end thereof to form a recess, aninsert portion of nickel-free metal in said recess having one end weldedto said one end of said first element to form a hot thermojunction, atubular fuel conducting member enveloping said tubular element andterminating in radial flame ports on one side of said therrnojunctionfor directing flame upon said projection adjacent said thermojunction,and a flame retaining plate of nickelfree metal positioned on theopposite side of said thermojunction from said llame ports, said platebeing welded to the opposite end of said portion and to said projectionleaving an unmelted section of nickel-free metal between said rstelement and the surrounding atmosphere.

References Cited in the file of this patent UNITED STATES PATENTS

